Prof. Takaaki Kajita

Nobel Laureate for Physics at the Institute for Cosmic Ray Research of the University of Tokyo/Japan, November 2023


Takaaki Kajita was born in 1959 in a small town with a long name: Higashi-Matsuyama, in Japan. The town is located roughly an hour north of Tokyo. Here he grew up in a peaceful environment, surrounded by rice fields.

Takaaki Kajita’s high school had a less structured curriculum, which allowed the students to pursue their own areas of interest. He liked studying thought rather than memorizing, especially with interest in physics, biology and earth science. He also spent a large amount of his youth playing a Japanese style of archery called Kyudo. Though he was admittedly not very good at Kyudo, he continued to practice it all throughout his time in high school and in university.

After high school Takaaki Kajita was admitted to Saitama University where he began studying physics. He became particularly interested in experimental physics, leading him to continue studying in graduate school. In April 1981 he joined future Physics Nobel Laureate Prof. Masatoshi Koshiba as a graduate student at the University of Tokyo.

Soon after Takaaki Kajita was asked by a fellow graduate student to begin working on the Kamiokande experiment at the Kamioka Observatory in Kamioka, Japan. The Kamiokande experiment was designed to detect the decay of protons. It attempted to do this by burying a large tank of pure water deep underground, which was connected to many specialized sensors that detected the photons generated when protons decay. These types of detectors must be buried deep underground to protect them from the cosmic radiation commonly found on the Earth’s surface.

Takaaki Kajita’s experience with the Kamiokande experiment caused him to choose a professional career in experimental physics. He wrote his doctoral dissertation on the early results of the Kamiokande experiment and received his Ph.D. from the University of Tokyo in 1986.

Dr. Kajita did not find immediate success as a professional physicist, as he was refused a research position with the Japan Society for the Promotion of Science shortly after receiving his degree. Fortunately Professor Koshiba offered him a position at the International Center for Elementary Particle Physics of the University of Tokyo.

After two years there Dr. Kajita’s experience on the Kamiokande experiment paid off. In 1988 he moved to the Institute for Cosmic Ray Research (ICRR) to work on the Kamiokande’s sequel, often called Super-Kamiokande.

Super-Kamiokande intended to build upon the results of the first experiment by building a much larger, more sensitive detector on the same site at the Kamioka Observatory. The project took years to design, and Dr. Kajita and his team collaborated with various groups in Japan and the USA to build it. Super-Kamiokande finally opened in 1996 after a year of underground construction work. Two years later Dr. Kajita made arguably the biggest discovery of his career.

His team at Super-Kamiokande found that when cosmic rays hit the Earth’s atmosphere, the resulting neutrinos switched between two flavors before they reached the detector under Mount Ikenoyama in Kamioka. This discovery proved the existence of neutrino oscillation and indicated that the Standard Model, which assumed neutrinos to be mass-less, is incomplete. For discovering the oscillations of neutrinos from one flavor to another, which proved that those subatomic particles have mass, he was awarded the Nobel Prize in Physics in 2015.

The experiments conducted by Professor Kajita and his colleagues have since become some of the most promising, powerful, versatile and efficient ways to explore both particle physics and the Universe itself.

Today Professor Kajita is a professor of the ICRR. He served as the Director of the ICRR between 2008 and 2022. He is also the principal investigator of another ICRR project located in Kamioka, the KAGRA gravitational wave project. Between 2020 and 2023 he was the President of the Science Council of Japan.

Topic of keynote speech:
  • The importance of science for peace-building

Monday, November 27, 2023:

14:00  Public keynote speech and dialogue at Chulalongkorn University in Bangkok
– Further information and free seat reservation: phone 02-218-3126, email, (

Wednesday, November 29, 2023:

14:00  Public keynote speech and dialogue at Prince of Songkla University in Songkla
– Further information and free seat reservation: phone 074-446-824, email (